There are known PGA sockets and LGA sockets for IC packages. As an example, European Patent Application Publication No. 1 006 618 discloses an IC socket for PGA packages. This IC socket comprises: an insulative base housing equipped with a great number of terminals (contacts) in a matrix arrangement, a slide member having a great number of through holes in a matrix arrangement above the base housing and sliding means for sliding the slide member on the base housing. An IC package which is compatible with this type of IC socket comprises a great number of lead pins that function as electrodes, which are embedded in a surface to be mounted onto the base housing in a matrix arrangement that corresponds to the terminals of the IC socket. When the IC package is mounted onto the base housing, the lead pins pass through the through holes of the slide member and reach the terminals. However, electrical connections are not established among the lead pins and the terminals at this point. A great amount of operational force is required to cause the lead pins and the terminals to contact each other to establish electrical connections therebetween because of the great number of lead pins involved. For this reason, mechanical means, such as the aforementioned slide member, is generally employed. The slide member causes the IC package to slide horizontally, thereby causing the lead pins and the terminals to contact each other.
U.S. Patent Application Publication No. 20040095693 discloses an IC socket for LGA packages. This IC socket comprises: an insulative inner housing (socket housing); a great number of terminals (contacts) provided in the inner housing in a matrix arrangement; a metal plate, on which the inner housing is mounted; an outer housing having an opening that accommodates the inner housing, provided on the metal plate; a cover member, which is pivotally mounted to one end of the outer housing so as to be rotatable with respect thereto; and a lever for locking the cover member onto the metal plate in a closed state, provided at the other end of the outer housing. The terminals in this type of IC socket protrude diagonally from the IC package mounting surface thereof, and the protruding portions are resiliently movable with respect to the mounting surface. Meanwhile, an IC package, which is compatible with this type of IC socket, comprises a great number of pads for contacting the terminals in a matrix arrangement. The cover member is placed over the IC package after the IC package is placed on the inner housing, and the cover member is driven to press the IC package against the inner housing by operating the lever. The cover member is locked in the closed position, thereby maintaining electrical connections among the pads of the IC package and the terminals of the inner housing in a pressurized state.
In the IC socket of European Patent Application Publication No. 1 006 618, the lead pins embedded in the PGA package are provided at high density with narrow pitch, and are therefore are extremely thin and prone to deformation due to external force. For example, if the IC package is inadvertently dropped, or is struck by an object, the lead pins deform easily. In addition, if the IC package is oriented in the wrong direction during mounting onto the IC socket, excessive force is imparted on the lead pins, and there is a possibility that they will be deformed. Even if the IC package is mounted in the correct orientation, there is a possibility that the lead pins will become deformed depending on the manner of operation, because the lead pins themselves function as insertion guides.
In the IC socket of U.S. Patent Application Publication No. 20040095693, LGA type IC packages are smaller than the IC package mounting surface of the inner housing, that is, the socket housing. Therefore, if the IC package is inadvertently dropped onto the socket housing during mounting thereof, there is a possibility that the IC package will strike the terminals of the socket housing and deform them.
In addition, in the case that the IC package is oriented in the wrong direction during mounting onto the IC socket, a finger that removes the IC package to remount it in the correction orientation may contact the terminals of the IC socket and deform them. Even in the case that the IC package is mounted in the correct orientation, a finger of an operator who is holding the IC package may inadvertently contact the protruding terminals of the IC socket and deform them, because the IC package is smaller than the IC package mounting surface of the IC socket.